The invention relates to an antenna structure, and more particularly to an antenna structure providing improved radiation pattern.
FIGS. 1a and 1b show an antenna structure 12 disclosed in U.S. Pat. No. 6,339,404, which comprises a substrate 14, radiation elements 22, a conductive element 24, a conductive element 26, a reflective element 28, impedance matching elements 46 and cables 44. The substrate 14 comprises a first surface 16 and a second surface 18. The reflective element 28 is disposed on the first surface 16. The radiation elements 22 are disposed on two sides of the reflective element 28. The cables 44 comprise conductive lines 42 and 48. The conductive lines 42 are coupled to the reflective element 28. The conductive element 24, the conductive element 26 and the impedance matching elements 46 are disposed on the second surface 18. The conductive element 24 and the conductive element 26 are connected to the impedance matching elements 46. The conductive lines 48 are coupled to the conductive element 24 and the conductive element 26.
Conventional antenna structure 12, however, comprises two conductive lines 48, two independent impedance matching elements 46 and two conductive elements 24 and 26, the structure thereof is complicated, and the radiation pattern cannot be improved by modifying the conductive line 48, or the conductive elements 24 and 26. Additionally, when a plurality of antenna structures 12 are connected in parallel to achieve an improved signal transmission, the size thereof is large.